Serving radio network controller (SRNC) relocation is an important feature in providing mobility in 3G communication systems. Relocation means a procedure where the routing of a user terminal connection in the Universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN) changes.
The relocation procedure is, however, a source of interruption in a user data flow due to switching functions between a drift RNC (DRNC) and a core network (CN). It is not possible to control the switching functions synchronously since there are propagation delays between RNC and CN as well as processing delays of signalling messages. Interruptions in the user data flow are undesirable especially in real time services, e.g. speech and circuit switched data.